Add new properties for Obsolete Attribute

src/libraries/System.Private.CoreLib/src/System/ObsoleteAttribute.cs

@@ -18,35 +18,39 @@ namespace System
     // Error indicates if the compiler should treat usage of such a method as an
     //   error. (this would be used if the actual implementation of the obsolete
     //   method's implementation had changed).
+    // DiagnosticId. Represents the ID the compiler will use when reporting a use of the API.
+    // UrlFormat.The URL that should be used by an IDE for navigating to corresponding documentation. Instead of taking the URL directly,
+    //   the API takes a format string. This allows having a generic URL that includes the diagnostic ID.
     //
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum |
         AttributeTargets.Interface | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Delegate,
         Inherited = false)]
     public sealed class ObsoleteAttribute : Attribute
     {
-        private readonly string? _message;
-        private readonly bool _error;
-
         public ObsoleteAttribute()
         {
-            _message = null;
-            _error = false;
+            Message = null;
+            IsError = false;
         }
 
         public ObsoleteAttribute(string? message)
         {
-            _message = message;
-            _error = false;
+            Message = message;
+            IsError = false;
         }
 
         public ObsoleteAttribute(string? message, bool error)
         {
-            _message = message;
-            _error = error;
+            Message = message;
+            IsError = error;
         }
 
-        public string? Message => _message;
+        public string? Message { get; }
+
+        public bool IsError { get; }
+
+        public string? DiagnosticId { get; set; }
 
-        public bool IsError => _error;
+        public string? UrlFormat { get; set; }
     }
 }

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -2898,7 +2898,9 @@ public ObsoleteAttribute() { }
         public ObsoleteAttribute(string? message) { }
         public ObsoleteAttribute(string? message, bool error) { }
         public bool IsError { get { throw null; } }
+        public string? DiagnosticId { get { throw null; } set { } }
         public string? Message { get { throw null; } }
+        public string? UrlFormat { get { throw null; } set { } }
     }
     public sealed partial class OperatingSystem : System.ICloneable, System.Runtime.Serialization.ISerializable
     {

src/libraries/System.Runtime/tests/System/ObsoleteAttributeTests.cs

@@ -14,28 +14,34 @@ public static void Ctor_Default()
             var attribute = new ObsoleteAttribute();
             Assert.Null(attribute.Message);
             Assert.False(attribute.IsError);
+            Assert.Null(attribute.DiagnosticId);
+            Assert.Null(attribute.UrlFormat);
         }
 
         [Theory]
-        [InlineData(null)]
-        [InlineData("")]
-        [InlineData("message")]
-        public void Ctor_String(string message)
+        [InlineData(null, null)]
+        [InlineData("", "BCL0006")]
+        [InlineData("message", "")]
+        public void Ctor_String_Id(string message, string id)
         {
-            var attribute = new ObsoleteAttribute(message);
+            var attribute = new ObsoleteAttribute(message) { DiagnosticId = id };
             Assert.Equal(message, attribute.Message);
             Assert.False(attribute.IsError);
+            Assert.Equal(id, attribute.DiagnosticId);
+            Assert.Null(attribute.UrlFormat);
         }
 
         [Theory]
-        [InlineData(null, true)]
-        [InlineData("", false)]
-        [InlineData("message", true)]
-        public void Ctor_String_Bool(string message, bool error)
+        [InlineData(null, true, "")]
+        [InlineData("", false, null)]
+        [InlineData("message", true, "https://aka.ms/obsolete/{0}")]
+        public void Ctor_String_Bool_Url(string message, bool error, string url)
         {
-            var attribute = new ObsoleteAttribute(message, error);
+            var attribute = new ObsoleteAttribute(message, error) { UrlFormat = url };
             Assert.Equal(message, attribute.Message);
             Assert.Equal(error, attribute.IsError);
+            Assert.Null(attribute.DiagnosticId);
+            Assert.Equal(url, attribute.UrlFormat);
         }
     }
 }